What is the BCG vaccine and why is it given?
The BCG vaccine is the only TB vaccine currently available, although there are other vaccines under development. The BCG vaccine is still the only vaccine available for the prevention of human forms of TB. The BCG vaccine is relatively inexpensive, safe, and usually readily available.
Who is given the BCG vaccine?
The BCG vaccine is normally given to children as it has been shown to provide very good protection against the disseminated forms of TB in children, including meningitis. However the protection provided against pulmonary TB in adults is very variable. So the vaccine is not generally given to adults.1“Immunization surveillance, assessment and monitoring”, WHO www.who.int/immunization_monitoring/diseases/tuberculosis/
The BCG vaccine is one of the most widely used of all current vaccines, and overall it reaches more than 80% of all new born children and infants in countries where it is part of the national childhood immunization programme.2“BCG vaccine”, WHO
www.who.int/biologicals/areas/vaccines/ The World Health Organisation (WHO) monitors the estimated coverage of the BCG vaccine in every country. 3“Estimates of BCG coverage”, WHO
Not every country that could do so gives the vaccine to all children. Generally countries where there is a high level of TB use the vaccine to vaccinate all children. Some countries with a low level of TB, such as the United States and England do not give all children the vaccine, but only those considered at particular risk. The United States has never vaccinated all children, but in the United Kingdom all children were given the vaccine until 2005.4“The BCG World Atlas”,
The vaccine and the TB skin test
People who have had the vaccine will often then have a positive result to a TB skin test. This makes it more difficult to establish whether someone has latent TB. This is one of the reasons that the vaccine is not used in some countries.5“When is the BCG (TB) vaccine needed? - Vaccinations - NHS Choices”, NHS choices www.cdc.gov/tb/topic/testing/
The skin test will often be given before vaccination. If there is a positive result to the skin test then the vaccination will not be given.6“BCG (tuberculosis) vaccination - When it is needed”, NHS Choices, www.nhs.uk/Conditions/BCG/Pages/When-it-is-needed.aspx
BCG vaccine safety issues
In the early years of the use of the vaccine there were some concerns about safety, and there was the Lubeck disaster. Subsequently for many years there was little concern about safety. However it is now considered that the use of the vaccine in children who are immune compromised, such as children with HIV, could result in them having an infection caused by the BCG vaccine itself. This is because the vaccine contains a live but very weakened form of a bacteria called Mycobacterium bovis. This is not the same bacteria though as the bacteria that causes TB in humans, which is called Mycobacterium tuberculosis.7BCG - the current vaccine for tuberculosis, WHO
www.who.int/vaccine_research/diseases/tb/vaccine_development 8“The Difference Between Latent TB Infection and Active TB Disease”, CDC, www.cdc.gov/TB/publications/factsheets/general/LTBIandActiveTB.htm
BCG immunization generally causes some slight pain and scarring at the site of the injection.
Replacing the vaccine
The organisation AERAS was set up in 2003 to develop new, safe, effective and affordable vaccines to replace the BCG vaccine. A new vaccine will need to protect against all strains of TB including the different types of drug resistant TB. The vaccine will also need to be suitable for use in preventing TB in children, adolescents and adults, as well being safe for use in people who are infected with both HIV and TB.9“AERAS - Global Efforts”, AERAS
AERAS is supporting the clinical testing of six possible new TB vaccines any one of which could be a suitable vaccine to replace BCG. In October 2012 it was announced that in connection with Glaxo, AERAS will in 2013 begin a phase IIB study in Kenya, India and South Africa. It is planned that this vaccine if successful would be used alongside the existing BCG vaccine.10“Aera, GSK will test TB vaccine in India and Africa”, Vaccine News Daily, October 12 2012
Another potential TB vaccine also designed to be used in conjunction with BCG is MVA85A. In February 2013 the results were announced of a phase 2B trial of MVA85A.11“Safety and efficacy of MVA85A, a new tuberculosis vaccine, in infants previously vaccinated with BCG: a randomised, placebos-controlled phase 2B trials”, The Lancet, February 4 2013 www.thelancet.com/ This disappointingly showed that MVA85A did not provide any significant effectiveness against either tuberculosis or M. tuberculosis infection, although some people considered that:
“the findings … are not a terminal prognosis for MVA85A, or for any of the other tuberculosis vaccines in development.”12“A major event for new tuberculosis vaccines”, The Lancet, February 4 2013 www.thelancet.com/
More recently encouraging news has come about a potential vaccine that appears to be effective in adults already infected with TB bacteria, which are the cause of TB. But it will have to go through more trials and it will probably be at least 2028 before it is ready.13Soutik Biswas, 'Game changing' tuberculosis vaccine a step closer, 2019, https://www.bbc.co.uk/news/world-asia-india-50205762
This page was last updated in December 2019.
Author Annabel Kanabus
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